Dynamics of the malaria-vector populations in coastal Lagos, south-western Nigeria
Awolola, T.S.; Okwa; Hunt, R.H.; Ogunrinade, A.F.; Coetzee, M.
Annals of Tropical Medicine and Parasitology 96(1): 75-82
2002
ISSN/ISBN: 0003-4983 PMID: 11989536 DOI: 10.1179/000349802125000538Document Number: 236152
An entomological study was carried out in coastal Lagos, south-western Nigeria, to explore the role of Anopheles gambiae s.l. and A. moucheti in the transmission of Plasmodium falciparum in this holo-endemic area. Mosquitoes were caught, on human bait at night and by pyrethrum-spray catches during the day, twice a month throughout 2000. Of the 1812 Anopheles mosquitoes collected, A. gambiae s.l., the predominant vector species, represented 78.7% while the other 21.3% were A. moucheti. The results of a PCR-based test identified 56.8% of the mosquitoes of the A. gambiae complex collected as A. gambiae s.s., 36.9% as A. melas and 6.3% as A. arabiensis. A. gambiae s.s. was predominantly recorded in the wet season, biting females being collected from May to October, with a peak in July. A. melas and A. moucheti were present throughout the year-long study whereas A. arabiensis was mainly found in the dry season. The results of ELISA-based analyses of bloodmeals indicated that A. gambiae s.s., A. melas and A. moucheti were predominantly anthropophagic whereas A. arabiensis was largely zoophagic. Among all of the females investigated, 3.6% of A. gambiae s.s., 1.9% of A. melas, 1.8% of A. moucheti and 0% of A. arabiensis were infected with P. falciparum (i.e. carrying the parasite's circumsporozoite antigen). The corresponding proportions for the females collected during the dry season were 1.3%, 2.3%, 2.7% and 0%. The entomological inoculation rates for A. melas and A. moucheti were significantly higher during the dry season than at other times of the year. Taken together, these results indicate that A. melas and A. moucheti maintain transmission of P. falciparum during the dry season, while the biting population of A. gambiae s.s. is relatively small.